Through patent searching, Joint Action Warning of Gas Water Heater in Chinese utility model patent 00237346.7 publishes a kind of circuit that can integrally process joint actions and auto-control on gas water heaters, ventilation equipment and gas-leaking and excessive exhaust gas warning. The circuit has realized the function that the leaking sensor works intermittently under the control of timing circular circuits. The water heater will be turned off after excessive exhaust gas is warned and the ventilation equipment will be run after gas-leaking is warned. Besides, Gas-leaking Protector of Gas Water Heater with an External A/D Convertor in Chinese design patent application 200510049317.5 provides a kind of gas-leaking protector of gas water heater with an external A/D convertor, through the external A/D convertor; gas sensor output is connected with the I/O input port of single-chip computer in water heater controller. Then the water heater controller is connected with the valve and warning circuits, achieving that the single-chip computer will cut off the gas source and warn when the gas is exceeded.
Searching oversea related patents show that although The Controlling System of Gas Water Heater disclosed by American Patent U.S. Pat. No. 5,797,358 has provided a controlling system that gas sensor, CO sensor and water heater processor are electrically connected, the above described problems still exist in the technology.